C code

// You can run a larger C program (FizzBuzz) by changing this condition.
// Note you may not want to do this for slower backends (e.g., Brainfuck).
#if 1
int putchar(int c);

int main() {
  const char* p = "Hello, world!\n";
  for (int i = 0; i < 20; i++)
    putchar(p[i]);
  return 0;
}

#else

int putchar(int c);

int div(int a, int b){
  int result = 0;
  while(a >= b){
    a -= b;
    result++;
  }
  return result;
}

int mod(int a, int b){
  int result = 0;
  while(a >= b){
    a -= b;
  }
  return a;
}

const char* str = "FizzBuzz";

void fizz() {
  for (int i = 0; i < 4; i++)
    putchar(str[i]);
}

void buzz() {
  for (int i = 4; i < 8; i++)
    putchar(str[i]);
}

int isDivisible(int a, int b){
  return mod(a, b) == 0;
}

int printNum(int num){
  if(num >= 10){
    putchar(48 + div(num, 10));
  }
  putchar(48 +  mod(num, 10));
}

int main() {
  for (int i = 1; i <= 10; i++) {
    int div5 = isDivisible(i, 5);
    int div3 = isDivisible(i, 3);
    if(div3 && div5){
      fizz(); buzz();
    }else if(div3){
      fizz();
    }else if(div5){
      buzz();
    }else{
      printNum(i);
    }
    putchar('\n');

}
  return 0;
}

#endif

Transfer to Figma prototype

Compiler/assembler